Inhalation of toxic mineral particles causes acute injury to alveolar macrophages and several types of chronic lung disease including pulmonary fibrosis, increased susceptibility to tuberculosis, and an increased incidence of cancer. The objectives of this research are first, to determine the mechanisms of acute mineral particle toxicity and second, to describe the pathogenesis of the chronic complications resulting from exposure to toxic mineral particles. To explore the first objective, a model system using the mouse macrophage cell line P388D1 in vitro has been developed. Experiments are proposed to identify biochemical and structural changes in P388D1 cells injured by asbestos. The following changes will be evaluated as necessary or sufficient conditions responsible for irreversible injury in this model system: 1) oxidative damage to membrane proteins and lipids, 2) depletion of cellular antioxidants, 3) direct changes in membrane structure produced by toxic mineral particles, and 4) altered cytoskeletal organization. The extent of oxidative damage and antioxidant depletion resulting from asbestos exposure will be determined by biochemical assays. Changes in membrane structure and cytoskeletal organization will be detected by high resolution electron microscopy combined with freeze-drying, deep-etching with rotary replication, and critical point drying techniques. To explore the second objective, an in vitromodel system will be developed using co-cultures of primary mouse mesothelial cells and peritoneal macrophages exposed to asbestos. The extent of mesothelial injury will be assessed by the biochemical and structural procedures described in the first model. These experiments should determine whether asbestos fibers directly damage mesothelial cells or whether mediators released from injured macrophages are indirectly responsible for mesothelial reactions to asbestos fibers.